Differential response of rat splenic lymphocytes to short-term and long-term neuroendocrine challenges: possible desensitization of the cellular immune response to corticosteroids.

The effects of acute or chronic in vivo or in vitro exposures to supra-physiologic doses of isoproterenol, insulin or dexamethasone on rat splenic lymphocyte proliferation were investigated. Acutely, all in vivo challenges inhibited mitogen-induced lymphocyte proliferation, and correlated to increased corticosterone levels. However, chronic in vivo exposure to dexamethasone resulted in lymphocyte activity which was equivalent to controls, while chronic isoproterenol treatment enhanced the lymphocyte response to mitogen. These data suggest that chronic stress may result in a desensitization of the immune system to corticosteroids as well as a direct in vivo modulation by isoproterenol to enhance lymphocyte proliferation.